Very young children's responses to the emotional states of other persons and to simulations of these emotions were recorded. Mother-child pairs were observed for a 9-month period beginning when the child was 9, 15, or 21 months. Trained mother observers and trained researchers collected the data. At a very young age children respond with comfort to another's distress. In the age period studied this response became more frequent taking increasingly varied and elaborate forms. Some affectively expressed distresses provided stronger provocation for comfort than others: another's cry was most compelling, followed by expressions of physical pain, then the more minor physical discomforts. The person expressing the affect and the mode of expression, too, influenced the likelihood of compassionate gestures from the child. Affective expressions of distress were not always followed by altruistic acts. The plight of the other person was sometimes ignored, treated with indifference, or, in some instances, was the occasion for amusement or annoyance. A particularly prevalent response pattern was the child's imitation or "trying on" of the affective expression.